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Aggressive kudzu vine migrates northward

No B.C. sightings yet, ministry says, while warning of potential damage

Kudzu has been called the vine that ate the South.

Now it's the North's turn to struggle with it.

Kudzu patches have been reported in various Ohio counties, said Kathy Smith, Ohio State University Extension program director in forestry. In fact, it's been found as far north on this continent as Ontario.

The B.C. Ministry of Agriculture says kudzu has not yet been found in this province, but its website, kudzu.htm, carries a warning about the plant and a description of the damage it can do. A photograph of an abandoned house completely covered by thick vines gets the point across.

That doesn't necessarily mean the aggressive vine will soon drape northern U.S. and Canadian hillsides and choke all the trees. It's believed the growing season in some northern climes is too short to allow the plant to flower and produce fruit, which keeps kudzu from spreading rampantly.

But that could change, said James Bissell, curator of botany at the Cleveland Museum of Natural History.

The changing climate is warming our winters and stretching our growing season. Eventually, the conditions could become ripe for kudzu to flourish in northerly areas.

"With global climate change, it could be a problem," said Bissell, who tracks the distribution of plants in Ohio. "I expect it will be a problem."

Kudzu, or Pueraria mon-tana, is a perennial climbing vine native to Asia. It was introduced to the U.S. as an ornamental plant at the Philadelphia Centennial Exposition in 1876 and has also been grown as forage for livestock.

Its biggest boost, however, probably came from the U.S. Soil Conservation Service, which in the 1930s and '40s promoted its use for erosion control and even paid farmers to plant it.

Without the natural controls found in its native range, the vine grows prolifically, gaining as much as a foot a day in the hot South and spreading underground via a stout, deep root system. Andrew Londo, coordinator of extension forestry with Mississippi State University, said he has a photo of one particularly large kudzu tuber that "looks like something you'd see on a logging truck."

The vine blankets just about everything in its path, including fences, buildings, trees and power lines. It smothers other plants and sometimes breaks off their branches or uproots them.

Kudzu is already becoming a problem in the Ohio River valley, where the climatic conditions allow the plant to produce fruit. The seeds are spread by wildlife and even by mowers, vehicle tires and shoes.

In the Ohio area, the vine dies back to the ground in winter, but the root system remains alive, said Rick Gardner, a botanist with the Ohio Department of Natural Resources' Division of Natural Areas and Preserves. That winter die-back slows the plant's growth but does not stop it.

Even though kudzu is still uncommon, Bissell and other invasive plant specialists hope people will keep an eye out for the vine and report suspicious patches - a message British Columbians are also hearing from the provincial government.

The plant has compound leaves made of three leaflets that form a roughly heart-shaped cluster. The leaflets grow up to 20 centimetres long and about 10 cm wide, and they're green to yellow-green on the upper side and pale green beneath.

In areas where the growing season is long enough, the plant produces spikes of purple flowers and hairy seed pods five cm long.

Controlling the plant is challenging. A small infestation can be kept from spreading by cutting it or allowing livestock to graze on it, Smith said. But killing the plant requires chemicals, she said.

Mississippi state's Londo said herbicides can be effective, but must be applied by a certified professional.

It pays to prevent this vine from getting a roothold in B.C. in the first place rather than trying to get rid of it after the fact.

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